Arrangements are well known by which fluid is dispensed from fluid containing reservoirs. For example, known hand soap dispensing systems provide reservoirs containing liquid soap from which soap is to be dispensed. When the reservoir is enclosed and rigid so as to not be collapsible then, on dispensing liquid soap from the reservoir, a vacuum comes to be created in the reservoir. It is known to provide one-way valves which permit atmospheric air to enter the reservoir and permit the vacuum in the reservoir to be reduced. The one-way valves typically operate such that the one-way valve prevents air from entering the reservoir unless a vacuum is developed to a certain level below atmospheric pressure. To the extent that the vacuum increases beyond this certain level, then the valve will open permitting air to enter the reservoir and thereby prevent the vacuum from increasing further.
The provision of vacuum relief valves is advantageous not only in enclosed reservoirs which are rigid but also with reservoirs that may not so readily collapse as to prevent the development of a vacuum within the reservoir on dispensing.
The present inventor has appreciated that reducing the ability of vacuum conditions to arise in any reservoir can be advantageous so as to facilitate dispensing of fluid from the reservoir, particularly so as to permit dispensing with a minimal of effort and with a pump which has minimal ability to overcome any vacuum pressure differential to atmospheric pressure.
U.S. Pat. No. 5,676,277 to Ophardt which issued Oct. 14, 1997 discloses in FIG. 10 a known one-way valve structure in which a resilient flexible seal member is biased to close an air passageway such that on the development of vacuum within a reservoir, the seal member is deflected out of a position to close the air passageway and permits atmospheric air to enter the reservoir relieving the vacuum. Such flexible seal members suffer the disadvantage that they are subject to failure, do not always provide a suitable seal, and to be flexible must frequently be made from different materials than the remainder of the value structure. As well as insofar as a flexible seal member is to be maintained in contact with fluid from the reservoir, then difficulties may arise in respect of degradation of the flexible sealing member with time. As well, the flexible sealing member typically must experience some minimal level of vacuum in order to operate and such minimal level of vacuum can, in itself, at times present difficulty in dispensing fluid from the reservoir.
Most known soap dispensers suffer the disadvantage that they do not provide for inexpensive simple and/or energy efficient systems to dispense fluid, particularly when the systems are for automatically dispensing fluids with motor driven pumps. As a further disadvantage, known systems which use motor driven pumps do not permit for manual dispensing of the liquid as an alternative to dispensing with the motor driven pump as, for example, in the situation where the pump is inoperative. The pump may be inoperative as, for example, by reason of malfunction of the pump mechanism or the loss of power as, for example, under power failure conditions or if batteries to drive the pump have become depleted.